The present invention is an improvement of the inventor's invention applied for a Letter Patent under Ser. No. 721,369 filed on April 9, 1985 which you notified your approval of patent granting on Oct. 28, 1985. The structure in the said invention mainly involved the use of a thrust bearing fixed to a socket for a plurality of steel rods so that the socket will not rotate following rotation of the ground anchor and connecting tubes to penetrate the ground anchor can be recovered one by one, only the steel rods and anchor head will be left behind in the earth in order to increase holding force of the ground anchor. However, if the ground anchor is to be extended to neighbor land belonging to any other party, recovery of the steel rods will be very difficult since they are welded to the fixing holes of the socket. Furthermore, the inventor's prior invention disclosed an anchor head structure with a plurality of curved swingable arms hinged at appropriate position. When the swingable arms are closed, the swingable arms are tightly held around the rear end of the anchor head. It is necessary to withdraw the ground anchor to a certain extent or to flush them with water to help their extension. Their extension will encounter problem if they are in earth with considerable hardness, and there is a considerable friction between their curved external surfaces and the earth during the extension. The prior invention has a drill bit fixed to the front end of the anchor head with a spring and a spring-loaded ball between the drill bit and the front end to prevent from back flow of ground water. The spring and spring-loaded ball are unnecessary for application at any place without ground water.